<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 100%;
            height: 60px;
            line-height: 60px;
            text-align:center;
            border: 1px soild ;
            background-color: blue;
            color: blueviolet;
            font-size: 18px;
        }
    </style>
</head>
<body>
    <div>
        广告
    </div>
    <script>
        var div =document.querySelector('div');
        setTimeout(function(){
          div.style.display='none';
        },5000)
    </script>
</body>
</html>